02 dicembre 2014
What and Why
A quick background:
- Among young adults (15-29), suicide accounts for 8.5% of all deaths: second leading cause of death (after traffic accidents).
Among adults (30-49) suicide accounts for 4.1% of all deaths: fifth leading cause of death (latest "Prevent Suicide" report by WHO).
"The debate about the impact of climate change on human health has, very recently, included consideration of mental health" (Berry, Bowen & Kjellstrom, 2009).
The mental health vs climate relationship still needs to be studied into details (research gap).
Research question:
How do climate factors affect suicide rate in the Italian context?
- Is suicide rate lower whereby the average temperature is higher?
- Is suicide rate higher whereby the average temperature range is higher?
- Is suicide rate higher whereby precipitations happen more frequently?
Methodology
Case selection:
Previous study: regional data, 20 observations, unsignificant model.
Now, Italy is still our focus: county-level data provide 110 observations!
<<<<<<< Updated upstream
Our Model:
\[ <<<<<<< Updated upstream StdSuicideRate = \alpha + \beta_{1}GdpPerCapita + \beta_{2}Unemployment ======= SuicideRate = \alpha + \beta_{1}GdpPerCapita + \beta_{2}UnemploymentRate >>>>>>> Stashed changes \] \[ + \beta_{3}Population + \beta_{4}GiniIndex + \beta_{5}AverageTemperature \] \[ + \beta_{6}AverageTemperatureRange + \beta_{7}AveragePrecipitations + e \]
A Second, improved, model:
\[ <<<<<<< Updated upstream StdSuicideRate = \alpha + \beta_{1}GdpPerCapita + \beta_{2}Population \] \[ + \beta_{3}AverageTemperature + \beta_{4}AveragePrecipitations + e \]
Results
Models Comparison:
| First Model | Second Model | |
|---|---|---|
| GDP per capita*** | GDP per capita*** | |
| Unemployment Rate | dropped | |
| Population*** | Population*** | |
| Gini index | dropped | |
| Avg Temperature | Avg Temperature | |
| Avg Temp. Range | dropped | |
| Avg Precipitations*** | Avg Precipitations*** | |
| Dependent variable: | ||
| St. suicide rate | ||
| (1) | (2) | |
| GDP per capita | 0.699*** | 0.529*** |
| (0.211) | (0.117) | |
| Unemployment rate | 0.086 | |
| (0.106) | ||
| Population | -0.174*** | -0.158*** |
| (0.043) | (0.039) | |
| Gini index | 0.173 | |
| (0.487) | ||
| Average Temperature | -0.072 | -0.069 |
| (0.097) | (0.092) | |
| Temperature range | -0.066 | |
| (0.211) | ||
| Average Precipitations | -0.435*** | -0.461*** |
| (0.147) | (0.143) | |
| Constant | 5.312*** | 5.622*** |
| (1.415) | (1.123) | |
| Observations | 103 | 103 |
| R2 | 0.372 | 0.365 |
| Adjusted R2 | 0.326 | 0.339 |
| Residual Std. Error | 0.264 (df = 95) | 0.261 (df = 98) |
| F Statistic | 8.041*** (df = 7; 95) | 14.090*** (df = 4; 98) |
| Note: | p<0.1; p<0.05; p<0.01 | |
Findings:
Average temperatures and Temperature range have no impact on suicide rate across Italy
GDP per capita has a positive impact on suicides (in Italy).
Population size has a negative impact on suicides.
Annual precipitations has a negative impact on suicides.
Predicted Probabilities:
Conclusion:
Climate characteristics do affect suicide rates in Italy.
Correlation not as strong as (we) would have expected.
Rain actually has a negative impact on suicidial behaviour (contrary to what is commonly believed).
A one percentage increase in average precipitations decreases suicide rate by 0,461 percent.
Limitations and Further Research:
Data: only 2009. Panel data analysis?
Further applications to test whether precipitations and sucide rates are negatively correlated also in other developed countries.
Test other climatic factors (e.g. solar radiation)?
Test it with monthly data looking for seasonal patterns for suicide.
Thank you for your attention!
Conclusion
-Climate characteristics affect suicide rates in Italy -Correlation not as strong as (we) would have expected -Rain actually has a negative impact on suicidial behaviour (contrary to what is commonly believed)